Drafting instrument.



W. R. PEARSON.

DRAFTING JNSTRUMENT.

- APPLICATION FILED NOV. 3. 1913. 1,1 91,990. Patented July 25, 1916.

2 SHEETS-SHEET 1.

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W. R. PEARSON.

DHAFTING INSTRUMENT.

APPLICATION FILED nov. 3. 191a.

Patented July 25, 1916.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

WILLIAM REW PEARSON, OF SHERIDAN, OREGON.

DRAFTING INSTRUMENT.

Application filed November 3, 1913.

ment which may be employed in various ways and for various purposes after simple adjustments have been made.

It is one aim of theinvention to provide an instrument which 'may be employed in determining the center of any circular, cylindrical, or other curvilinear figure or object. 7 Another aim of the invention is to provide an instrument which may, not only be employed forthe purpose above stated, but may also be used as a T-square and as a protractor.

For a full understanding of the invention reference is to be had to the following description and accompanying drawing, in which .7

Figure 1 is a perspective view of the instrument embodying the present invention. Fig. 2 is. a vertical longitudinal sectional view on the line 22 of Fig. 1. Fig. 3 is a vertical section onthe line of Fig. 1. Fig. at is a bottom plan view of the instrument. Fig. 5 is a diagrammatic View illustrating the manner in which the instrument is to be employed in determining the center of a circle. Fig. 6 is a plan view of the in strument illustrating an attachment. therefor. Fig. 7 is a sectional View on the line 7-7 of Fig. 6. Fig. 8 1s a group perspective view illustrating certain of the parts about to be assembled.

Corresponding and like parts are referred to in the following description and indicated in all the views of'the accompanyingdrawing by thesame reference characters.

In the drawings, the body of the instrument is illustrated as flat sided and of frame like structure, it including a head 1 having a straight edge 2 from which pro ects an arm 3 occupying the sameplane as the head 1 and formed witha longitudinally extending slot 1. The arm 3 extends at right angles from the edge 2 of the head land has straight edges 5 and 6 which permit of the body being employed as a T-square, or

Specification of Letters Patent.

Patented July 25, 1916.

Serial No. 798,980.

ject from the under side of the head 1 and these studs are located in a line parallel to the edge 2 of the said head and are equi-distantly spaced from the edge 6 of the arm 3 so that a line drawn at this edge will be exactly midway between the studs 9. To reinforce the arm 3 and also to prevent tilting of the body when used as a T-square, a

bracing arm 10 is formed integral with the head 1 and the end of the arm 3 and is located opposite the edge 5 of the said arm and is preferably curved substantially as shownin the drawings so that the instrument may also be employed in drawing curved lines, if desired.

Inorder to adapt the instrument for use as a protractor, an attachment is provided which includes an annular head 11 having a cross-piece12 which is formed with an opening 13. The annular head. and cross-piece are formed upon their under sides with lugs 14: which are located in a line at right angles to the cross piece 12 and which slidably fit within the slot 4 in a manner clearly shown in Figs.-2, 3 and at of the drawings, when the attachment is in place upon the body of the instrument. Fitted through the opening 13 is the threaded shank 15 of a clamping bolt, the end of which is notched as at 16 and formed with a head 17 which projects a short distance laterally beyond the shank 15. By referring to Fig. 3 of the drawing it will be observed that after the bolt has been so applied to the arm 3 that the edge portion 6 of the arm may be received in the notch 16 and the head 17 will project beneath the said portion of the arm, the annular head 11 may be disposed upon the bolt with the lugs ll sition resting upon the upper side of the head 11, a clamping nut 21 is threaded onto the clamping bolt and serves to bind the will be apparent that the arms of the protractor may be angularly adjusted about the bolt as a center and may be held at adjustment by tightening the clamping nut. It is preferable that the arms 18 be provided with scale marks 22 denoting inches and fractions of inches and the annular head ll is provided with an annular series of scale marks 23 indicating various angles. By re-' ferring to Figs. 4: and 6 of the drawing it will be apparent that the non-corresponding but co-extensive edges of the arms 18 extend in a line transecting the axis of the clamping bolt 15 and that the opening 13 is located axially of the said head so that the said edges of the arms may indicate angles at opposite sides of a vertical line or above and below a horizontal line.

From the foregoing description of the invention and from an inspection of Fig. 5 of the drawings it will be seen that when the instrument is to be used for the purpose of finding the center of a circle, such for example as the end of a shaft to be trued or the end of a cylindrical object, the attachment is removed and the body of the instrument is disposed against the object with the studs 9 resting against the circumference of the perimeter thereof and a line is then drawn along the edge 6 of the arm 3. The instrument is then shifted so that the studs 9 will engage against the ob- ,ject at other points and another line is drawn. This may be repeated a number of times until the point if intersection of all of the lines determines definitely the center of the circle The manner of using the instrument as a T-square or as a curve will be readily understood and also the manner of using the same as a protractor.

In the form of the invention shown in Figs. 6 and 7 of the drawings the arms of the protractor are provided with an attachment in the nature of an arm 24 having a head 25 provided with flanges 26 which embrace the edges of that one of the arms 18 to which the head is applied, it being understood that the head is slid upon the said arm 18. It will be apparent that the arm 24 extends at right angles from the marking edge of the arm 18 to which it is applied.

Having thus described the invention what is claimed as new is 1. In an instrument of the class described, a head, an arm extending from the head and having a straight edge, a protractor head longitudinally adjustably mounted upon the said arm, an angle indicating arm angularly adjustable upon the protractor head, and an arm slidably mounted upon the angle indicating arm and extending laterally therefrom.

2. In a device of the class described, a head, an arm extending from the head and having a straight edge, a protractor head disposed upon the arm, the arm being formed with a longitudinally extending slot and the protractor head being provided with means slidably engaging in the slot, a clamp having a head cooperating with the straight edge of the arm and provided with a threaded shank fitting axially through the protractor head, an arm supported for angular adjustment by the said shank, and a set nut threaded upon the shank and bearing against the arm. I

3. In a device of the class described, a head, an arm extending from the head and having a straight edge, a protractor head disposed upon the arm, I the arm being formed with a longitudinally extending slot and the protractor head being provided with means slidably engaging in the slot, a clamp having ahead cooperating with the straight edge of the arm and provided with a threaded shank fitting axially through the protractor head, an arm supported for angular adjustment by the said shank, and a set 'nut threaded upon the shank and bearing against the arm, the said set nut serving both to hold the clamp head in clamping engagement with the straight edge of the said arm and to hold the protractor arm at angular adjustment.

4. In an instrument of the class described, a head, an arm extending from the head and having a straight edge, the arm being formed with a longitudinally extending slot, a protractor head disposed against the arm and provided with means slidably engageable-in the slot in the said arm, a clamping member having a shank fitted axially through the head and having its axis perpendicular to the straight edge of the arm, the said member including a head engaging the straightedge of the arm, and a set nut threaded-upon th'eshank and clamping the protractor head to the said arm.

5. In an instrument of the class described, an arm having a straight edge, a protractor head disposed against the arm, cooperating means'upon the protractor head and arm.

thereto, and means f0.- holding the arm at adjustment, the portions of the arm at the opposite sides of its axis being relatively olfset, whereby each of said portions will have an edge extending radially with respect to the said axis of the arm.

7.' In a device of the class described, a head, an arm extending from the head and having a straight edge, a protractor head slidably mounted upon the said arm and held against rotation with respect thereto, an angle indicating member supported for angular adjustment upon the said protractor head and having arms extending radially from its center, and means for holding the protractor head at adjustment upon the first-mentioned arm and for holding the angle indicating member at angular adjustment with relation to the protractor head.

8. In a device of the class described, a head, an arm extending from the head and provided with a straight edge and with a slot extending parallel to the said straight edge, a protractor head disposed upon the said arm and provided with means projecting into and slidably fitting the slot in the arm whereby to prevent rotation of the protractor head with relation to the arm, the protractor head having an annular scale bearing portion, an angle indicating arm rotatably disposed upon the protractor head, a bolt having a shank fitted through the said angle indicating arm and through the said protractor head and provided with a recess receiving the straight edge portion of the first mentioned arm whereby the axis of the protractor head will be in registration with the said straight edge of the first mentioned arm, and a nut threaded upon the said bolt and bearing against the angle indicating arm and adapted to secure the same at adjustment with relation to the protractor head.

In testimony whereof I aflix my signature in presence of two witnesses.

WILLIAM REW PEARSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

